As the clock ticked down to a strike against two private bus lines in Queens on Monday and a larger one that could affect the entire system on Tuesday, the saber-rattling grew more severe.

“The strike threat is serious,” said union Vice President Neil Winberry, who represents workers on the private bus lines. “The whole city will shut down.”

If a deal isn’t reached tonight, Winberry said, his 750 workers would walk off the job, abandoning 50,000 riders.

“This is a shot across the bow. This is just to send a message out,” he said of the private-bus strike.

On a Web site, the union posted detailed instructions to bus employees on how to execute the walkout – which included making sure all passengers reach their destinations before buses are returned to depots, and not abandoning buses on the street.

If the contract isn’t settled by tomorrow, Winberry insisted all 34,000 Local 100 transit workers would walk, sending 7 million daily riders scrambling to get around.

Other union officials have said the strike might occur in phases. A final decision on the form of the strike is expected tomorrow night.

Meanwhile, Gov. Pataki – who selects 17 of the MTA’s 21 board members, including Kalikow – was pressuring the agency to reach a deal and avoid a strike, a source close to the governor’s office said.

The previous contract expired at 12:01 a.m. Friday. But after rejecting the MTA’s offer, the union pushed back the strike deadline to 12:01 a.m. Tuesday.

Kalikow said Friday the MTA’s offer was final. Toussaint – citing the authority’s $1 billion surplus – says the MTA will have to do better.